This application pertains to the art of telecommunications and more particularly to automated power distribution systems. The invention is particularly applicable to electric power distribution systems and will be described with particular reference thereto. It will be appreciated, however, that the invention has broader applications and may be used in distribution systems of many different types including utilities such as natural gas, water and the like.
Generally, an electric power distribution system comprises a plurality of substations which receive high voltage electric power in the range of 135-550 kilovolts. Each substation typically services approximately 6,000-10,000 customers and functions to drop the high voltage thus received to approximately 23 kilovolts or so and then supply this lower voltage to a plurality of primary distribution feeders. Connected to each of the primary distribution feeders are a plurality of distribution transformers which act to drop the 23 kilovolts to 220 volts or to some other common use voltage. Each distribution transformer, in turn, supplies this lower voltage by means of secondary distribution lines to a plurality of customer service lines which supply electrical power to homes, businesses, and other electrical service customers. In the past, it has been found desirable to place electronic devices at each electric service customer location for electronically reading or monitoring the electrical usage meter or for controlling the usage of electric power. Such electronic devices may be operably connected with the utility headquarters in a number of ways including telephone lines, radio communications, and the electric power lines themselves. Telephone communication is relatively high in cost because the tariff structure set by the telephone company would bill each meter reading or control function as a telephone call. Radio communications tend to have interference from buildings and other signals, be high in cost, and have problems with FCC licensing requirements. A low cost alternative is to utilize the power lines themselves. However, the unlike telephone and radio communication systems, power lines are not designed for high speed data communications.
Others have previously suggested using power lines to form at least a portion of a data communications link in an automated power distribution system. Generally, such systems would comprise a large computer at the electric power headquarters for receiving all the meter reading information, generating electric power bills, controlling various loads, and the like. The central computer is connected by a high speed data communications link with a so-called satellite computer disposed at each of the various substations. Each satellite computer is, in turn, in operative communication with remote modules located at the individual customer service locations associated with the particular substation involved. The satellite computers function to collect meter reading data from the individual remote modules and to supply load control commands thereto. In response to such load control commands, the remote modules can perform numerous work functions such as disconnecting the power supply from a hot water heater, air conditioner, or the like. These commands may also cause the remote modules to return meter reading data to the associated satellite computer. The meter reading data may take numerous forms including, for example, the number of units of power used, current cumulative meter reading, power usages by time of day, and the like. It has been further suggested in the prior art to supply relay units at each distribution transformer. These relay units function to relay commands, meter reading data, and the like between each satellite computer and the associated remote modules.
One problem with the above described prior art systems resides in the high cost per customer for implementation. The remote modules in these prior systems have required sophisticated electronics. Indeed, the remote modules often included micro or mini computers with a memory for the storage of data and processing circuitry for handling load control operations, meter readings, and the like between periods of communication with the satellite computer. This has resulted in a high cost per remote module and, hence, a relatively high cost per consumer. The use of relay units at each distribution transformer has further increased the cost per customer. Still another problem has been in the fact that a failure or malfunction of a relay unit undesirably isolates the associated remote modules from the satellite computers. This results in removal of some customer service locations from the data communications system.
The present invention contemplates new and improved apparatus which overcome all of the above problems and others. The invention provides an automatic distribution system which is economical and highly reliable in practical application.